An animal model has been developed by which intravascular fibrin deposition can be quantitated. This model is being used to study the biological properties and fate of fibrin monomer complexes, the mechanism of endotoxin induced intravascular coagulation and the role of leukocytes in fibrin deposition. Distinguishing features in the mechanism of fibrin-formation in DIC and venous thromboembolism are being studied. An electrophoretic technique by which the heterogeneous composition of plasma fibrinogen can be visualized and quantitated is being used to investigate fibrinogen catabolism and the concentration and composition of fibrinogen in various diseases. The unique composition found in the blood of patients with occlusive vascular disease with respect to their high concentration of lower molecular weight fibrinogen will be investigated. BIBLIOGRAPHIC REFERENCES: Lipinski, B., Gurewich, V., Nowak, A. and Wetmore, R.: The effect of heparin and dipyridamole on the deposition of fibrin-like material in rabbits infused with fibrin monomer or fibrinogen. Thrombos. Res. 5:343-358, 1974. Gurewich, V., Hyde, E. and Lipinski, B.: The resistance of fibrinogen and soluble fibrin monomer in blood to degradation by vascular plasminogen activator in comparison with streptokinase and urokinase. Blood (in press).